Turbulent Magnetohydrodynamic Jet Collimation and Thermal Driving
Abstract
Description
We have argued that magnetohydrodynamic (MHD) turbulence in an accretion disk naturally produces hoop-stresses, and that in a geometrically-thick flow these stresses could both drive and collimate an outflow. We based this argument on an analogy of turbulent MHD fluids to viscoelastic fluids, in which azimuthal shear flow creates hoop-stresses that cause a variety of flow phenomena, including the Weissenberg effect in which a fluid climbs a spinning rod. One of the more important differences between the Weissenberg effect and astrophysical jets is the source of power. In our previous analysis, we only considered the power due to the spin-down torque on the central object, and thus found that we could only drive an outflow if the central object were maximally rotating. Here we take into account the energy that is liberated by the accreting matter, and describe a scenario in which this energy couples to the outflow to create a thermodynamic engine.
To appear in proceedings of: 3-D Signatures in Stellar Explosions (A workshop honoring J. Craig Wheeler's 60th birthday, June 10-13, 2003, Austin, TX, USA)
To appear in proceedings of: 3-D Signatures in Stellar Explosions (A workshop honoring J. Craig Wheeler's 60th birthday, June 10-13, 2003, Austin, TX, USA)